Adaptive guard band for multiple heads of a data storage device

ABSTRACT

An adaptive guard band scheme is disclosed for a data storage device. In illustrated embodiments, the adaptive guard band scheme formats different guard band cylinders and track zeros for different heads depending upon a contact cylinder of the different heads. In an illustrative embodiment, the adaptive guard band scheme utilizes the contact cylinders for the heads and a no fly cylinder to determine track zero(s) and extended data zone(s) for select heads.

CROSS-REFERENCE TO RELATED APPLICATION

This application cross-references and claims the benefit of U.S.application Ser. No. 14/063,509, now pending on even date herewithentitled “ADAPTIVE GUARD BAND FOR IMPROVED DATA STORAGE CAPACITY”.

SUMMARY

The present application relates to an adaptive guard band scheme toincrease data storage capacity for a data storage device. In illustratedembodiments, different track zeros are formatted for different headsdepending upon a contact cylinder of the different heads to increasedata storage capacity. In an illustrative embodiment, an adaptive guardband algorithm utilizes the contact cylinders for the heads and a no flycylinder to determine the adaptive guard band cylinder and track zerofor different heads. In embodiments disclosed, the algorithm configurestrack zero for different heads based upon an optimum data storagecapacity determination utilizing available tracks for the differentheads. Other features and benefits that characterize embodiments of thepresent invention will be apparent upon reading the following detaileddescription and review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a data storage device configuredto implement an adaptive guard band algorithm or scheme for extendeddata storage capacity.

FIG. 2A illustrates an embodiment of a recording media including a guardband having a guard band cylinder at a logical block zero cylinder ofthe recording media.

FIG. 2B illustrates an embodiment of a recording media including anadaptive guard band having a guard band cylinder spaced from the logicalblock zero cylinder.

FIG. 3 illustrates an embodiment of an adaptive guard band algorithmimplemented through a controller assembly of a data storage device toformat a recording media with an adaptive guard band.

FIG. 4A is a flow chart illustrating an embodiment for implementing anadaptive guard band scheme.

FIG. 4B schematically illustrates a variable size or width for anextended data zone to provide threshold capacity.

FIG. 4C is a flow chart illustrating process steps for implementing avariable size or width extended data zone.

FIG. 5 illustrates an implementation of an adaptive guard scheme andextended data zone for increased data storage capacity.

FIG. 6A illustrates a guard band for head A of a data storage deviceincluding head A and head B.

FIGS. 6B-6C illustrate an embodiment of a guard band for head A andformat for an adaptive guard band for head B to provide extended datastorage as illustrated in FIG. 6C

FIG. 6D illustrates another embodiment of a guard band for head A and anadaptive guard band for head B to provide extended data storage.

FIG. 7 is a flow chart illustrating an embodiment for implementing anadaptive guard scheme for multiple heads of a data storage device.

FIGS. 8A-8B illustrate embodiments for formatting a different trackzeros for select heads of a multiple head data storage device.

FIG. 9 illustrates a flow chart for formatting different track zeros fordifferent heads of a multiple head data storage device.

FIGS. 10A-10B illustrate embodiments for formatting multiple track zerosfor different heads of a multiple head data storage device.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Data storage devices use heads including one or more transducerelements, to write data to a recording media or disc and read data fromthe recording media or disc. For ramp load/unload devices or contactstart/stop devices, the heads are supported on ramps or landing zones atan outer or inner diameter of the disc during non-operational periods.The heads are supported on the ramp or landing zone to limit damage tothe media. During a power-on sequence, the heads are moved off the rampor landing zone to a load/unload area at the outer diameter of the discwhere an air bearing surface of the head is pressurized for read/writeoperations. The load/unload area of the media is more susceptible todamage because of the higher risk of contact between the head and themedia as the head is unloaded from the ramp and pressurized or as thehead is loaded onto the ramp as the device is powered down. Damage tothe media in the load/unload area can result in loss of data if data isstored in the load/unload area. The foregoing is intended to provide anillustrative use of embodiments of the adaptive guard band disclosed inthe present application, but is not exhaustive of the use andapplication of the embodiment disclosed in the present application.Embodiments of the present invention provide solutions to these andother problems, and offer other advantages over the prior art.

The present application describes adaptive guard band schemes forproviding extended data storage for data storage devices 100 forexample, the data storage device 100 illustrated in FIG. 1. As shown inFIG. 1, the data storage device 100 includes a head 102 and a magneticrecording media 104. The head 102 including one or more transducerelements (not shown in FIG. 1) is positioned above the recording media104 to read data from and/or write data to the recording media 104. Inthe embodiment shown, the recording media 104 is a rotating disc orother magnetic storage media that includes a magnetic storage layer orlayers. For read and write operations, a spindle motor 106 (illustratedschematically) rotates the media 104 as illustrated by arrow 107 and anactuator mechanism 110 moves the head 102 between an outer diameter orcylinder 112 and an inner diameter or cylinder 113 of the disc 104 toposition the head 102 relative to data tracks 114 on the rotating media104.

Both the spindle motor 106 and actuator mechanism 110 are connected toand operated through drive circuitry 116 (schematically shown). The head102 is coupled to an actuator block 118 of the actuator mechanism 110through a suspension assembly which includes a load beam 120 connectedto an actuator arm 122 of the actuator block 118 for example through aswage connection. The actuator block 118 is rotationally coupled to aframe or deck (not shown) through a bearing 124 to rotate about axis126. Rotation of the actuator mechanism 110 or block 118 moves the head102 in a cross track direction as illustrated by arrow 128. The one ormore transducer elements of the head 102 are coupled to head circuitry130 through flex circuit 132 to encode and/or decode data as the discrotates. Drive circuitry 116 and head circuitry 130 are controlledthrough a controller assembly 134. The controller assembly 134 includesone or more hardware and software components to implement read and writefunctions of the device and interface with a host system 136 asschematically shown. The hardware includes memory and one or moreprocessor devices to store and implement algorithms or instructions ofthe device. Although FIG. 1 illustrates a single load beam 120 coupledto the actuator block 118, additional load beams 120 and heads 102 canbe coupled to the actuator block 118 to read data from or write data tomultiple discs of a disc stack as described herein.

As schematically shown in FIG. 1, a recording surface of the media 104includes a plurality of data tracks 114 spaced between the outerdiameter 112 and inner diameter 113 of the disc. The tracks 114 containembedded servo data or sectors to locate and position the head 102relative to cylinders of the disc. Typically, the servo sectors includea track address, a sector or segment address and servo data for trackfollowing. The servo data is encoded on the disc at the time ofmanufacture via a dedicated servo track writer or using self-servo trackwriting algorithms that use the data heads 102 of the data storagedevice to encode the servo data on the disc 104. Track density or tracksper inch (TPI) for a particular disc depends on the read/write headwidth, off-track performance or bit error rate (BER) and othercharacteristics of the device. Prior to formatting the device, variousmeasurements are used to determine optimum TPI or bits per inches (BPI)to format the media or disc.

Data on a disc is typically addressed using a logical block address(LBA) which corresponds to a physical location on the disc. The LBAaddresses are assigned to physical data blocks or sectors on the disc104 in numerical sequence beginning at a logical block zero cylinder.The LBA address, logical block zero cylinder and format data is storedin firmware or memory 138 of the controller assembly 134 to provide aphysical zone and cylinder location for logical blocks of data stored onone or more discs 104 of the device. The controller assembly 134includes algorithms and/or tables to convert the LBA to a physicalblock, or cylinder location on the disc. As shown in FIG. 2A, the discis divided into zones z₁-z_(n), including groups of adjacent trackshaving a similar number of data blocks or sectors for zone bitrecording. Zone z₁ proximate to the outer diameter 112 of the discincludes more data blocks or sectors about the circumference of the disccompared to zone z_(n) proximate to the inner diameter 113 of the disc.The increased number of data blocks or sectors at the outer diameter 112provides a higher bit recording rate at the outer diameter 112 than atthe inner diameter 113 of the disc 104.

As shown in FIG. 2A for ramp load/unload, the head 102 is supported on aramp 140 at the outer diameter 112 of the disc. The head 102 issupported on the ramp 140 off the media during idle or non-operationalperiods to limit damage to the media as a result of head contact withthe media. For operation, the heads 102 are unloaded from the ramp 140and are positioned via operation of the actuator mechanism 110 to readand write data to tracks 114 on the data storage media 104. Duringnon-operational periods, the head 102 engages the ramp 140 through aload tab 142 (illustrated schematically) coupled to the head 102 throughthe suspension assembly. For operation, the actuator mechanism 110rotates the head 102 away from the ramp 140 to a load/upload area of themedia or discs 104 to pressurize the air bearing surface of the head 102to provide a fly height for the head 102 for read/write operations. Thefly height of the head 102 is unstable in load/unload area and datastored in the load/unload area is more susceptible to corruption ordamage.

Typically, devices include a guard band zone 144, which is designated asa no data storage zone in the load/unload area to reduce data loss ordamage in the load/unload area proximate to the ramp 140. In theembodiment shown in FIG. 2A, the guard band zone 144 has pad width 145that is measured from a contact cylinder 146 where the head 102 contactsthe ramp 140 to a guard band cylinder spaced from the contact cylinder146. Contact is detected using a read-back signal from a read element148 on the head and the contact cylinder 146 corresponds to the track ofthe read element 148 of the head at which contact is detected.Formatting algorithms implemented through the controller assembly 134use contact data to format track zero 150, the guard band zone 144 anddata zones z₁-z_(n) for the disc. Track zero 150 is a first data trackof the recording media or disc accessed by the host 136 to read andwrite data. In the illustration shown in FIG. 2A, the disc is formattedso that track zero 150 and a logical block zero cylinder 152 for deviceis at a guard band cylinder spaced the pad width 145 from the contactcylinder 146. In the embodiment shown in FIG. 2A, the LBA addresses fordata are assigned to physical tracks or cylinders on the disc insequence beginning at the logical block zero cylinder 152 at track zero150.

Although allocation of the guard band zone 144 at the outer diameter orcylinder 112 of the disc for ramp load/unload devices, reduces the riskof data loss in the load/unload area, allocation of the guard band zone144 limits a data storage capacity of the device. As shown in FIG. 1,the present application implements an adaptive guard band algorithm 153to configure the firmware 138 of the device to provide an adaptive guardband zone 154 to increase data storage capacity as illustrated in FIG.2B. In the embodiment shown in FIG. 2B, the adaptive guard band zone 154has an adaptive pad width 155 smaller than the pad width 145 of theguard band zone 144 shown in FIG. 2A. Track zero 150 is defined at acylinder spaced from the contact cylinder 146 the reduced pad width 155to provide an extended data zone z₀ 156.

In the embodiment shown, the logical block zero cylinder 152 is spacedfrom track zero 150 to limit storage of sensitive data in the extendeddata zone z₀ 156. As schematically shown, the logical block zerocylinder 152 is spaced the pad width 145 from contact cylinder 146 andtrack zero 150 is spaced the reduced pad width 155 from the contactcylinder 146. The logical block zero cylinder 152 is spaced from trackzero 150 so that higher LBAs less frequency accessed are stored in theextended data zone 156. Critical and operating system data has lowerLBAs and is physically stored at outer diameter zones e.g. z₁ of thedisc beginning at the logical block zero cylinder 152. Use of theextended data zone to store higher LBA data avoids storage of operatingsystem and frequency accessed data in a zone more susceptible to damage.In the embodiment shown in FIG. 2B, the LBA for inner diameter zonez_(n) are mapped to the extended data zone z₀ 156 for physical storage.Although not shown, the extended data zone z₀ 156 can be extended closeto the head 102 so that a portion of the head is over the extended datazone 156 at the contact cylinder 146 of the ramp 140 to maximizeextended data storage.

As shown schematically in FIG. 3 the adaptive guard band algorithm 153formats the adaptive guard band 154 and extended data zone 156 utilizinginput capacity measurements 160 such as tracks per inch capacity TPICand margin, bits per inch capacity BPIC and the cylinder of logicalblock zero 152. The algorithm 153 uses TPIC and margin, BPIC and logicalblock zero cylinder 152 to determine the capacity of the device. If thedevice capacity is higher, then no extended data zone z₀ 156 isformatted and if the device capacity is lower, the adaptive guard band154 and extended data zone 156 is implemented through the firmware 138of the controller assembly 134 to format track zero 150 outward from thelogical block zero cylinder 152. As described, the adaptive guard bandalgorithm 153 is implemented through format instructions stored inmemory of one or more hardware components of formatting equipment toformat the discs during the manufacturing process.

FIG. 4A illustrates process steps for formatting the data storage deviceutilizing an embodiment of the adaptive guard band algorithm 153 basedupon the capacity of the device. As shown, in step 170, input capacitymeasurements are received and the data storage capacity of the device isdetermined utilizing the input measurements 160. As previouslydiscussed, the input capacity measurements include BPIC and TPIC toprovide the data storage capacity for zones z₁-z_(n) on the disc. Instep 172, the capacity of the disc for zones z₁-z_(n) is compared to athreshold data storage capacity. If the capacity of the disc or deviceis at or above the threshold capacity then the algorithm 153 does notformat an adaptive guard band zone 154 and extended data zone 156 forthe device as illustrated in step 174.

If the capacity does not meet the data storage capacity threshold, thenthe capacity of the disc or device having an adaptive guard band zone154 and extended data zone 156 is determined as illustrated in step 175.In step 176, the data storage capacity with the extended data zone 156is compared to the threshold capacity to determine if the data storagecapacity with the extended data zone is at or above the thresholdcapacity at step 177. If the capacity of the device with the extendeddata zone 156 meets the threshold capacity, then the disc or device isformatted with the extended data zone 156 as illustrated in step 178. Ifthe capacity of the disc or device with the extended data zone 156 doesnot meet the threshold capacity then the device is rejected or isdowngraded as illustrated in step 179. As described, the extended datazone 156 and adaptive guard band 154 improves manufacturing yield fordevices having the threshold data storage capacity.

As schematically shown in FIG. 4B, the size of the extended data zone156 is adjustable or variable depending upon the extended data storagecapacity required to meet the threshold capacity for the device. FIG. 4Bschematically illustrates four different extended data zones 156A, 156B,156C and 156D having different sizes or widths. The size of the extendeddata zones 156A, 156B, 156C, 156D is variable between the maximum sizeof the extended data zone at cylinder 180 and logical block zerocylinder 152. The smallest allowable pad width 155D for the device ismeasured from the contact cylinder 146 to cylinder 180. In theillustrated embodiment, extended data zones 156A, 156B, and 156C formmini-zones smaller than adjacent zones and the maximum sized extendeddata zone 156D at cylinder 180. Track zero 150A, 150B, 150C or 150D isformatted at cylinders spaced from logical block zero cylinder 152 thezone width for each of the extended data zone 156A-156D. Data isaddressed beginning at logical block zero cylinder 152 outwardly totrack zero 150A, 150B, 150C or 150D.

The mini-zones are sized to provide the additional data storage capacityto meet the required threshold capacity. Extended data zone 156Aprovides the least additional data storage capacity but the largest padwidth 155A. Extended data zone 156D provides the maximum additional datastorage capacity but the smallest pad width 155D.

FIG. 4C illustrates process steps for formatting the size of theextended data zone 155. In particular as shown in FIG. 4C, as previouslydescribed at step 177, the data storage capacity with the added extendeddata zone 156 capacity is compared to the threshold capacity todetermine whether to configured the media with the extended data zone orreject or downgrade the drive. In the illustrated embodiment, themaximum extended data storage capacity of zone 156D is used to determineif the data storage capacity of the drive meets the threshold capacity.If the maximum extended data zone capacity of zone 156D provides theadditional capacity to meet or exceed the threshold capacity then, theadditional storage capacity required to meet the threshold capacity iscalculated in step 182. The calculation uses the difference between thethreshold capacity and the measured storage capacity of zones z₁-z_(n)to determine the additional capacity required.

In step 184, the additional capacity calculated in step 182 is used todetermine a variable width or size of the extended data zone to formattrack zero 150 in step 186 at the cylinder corresponding to thedetermined width of the extended data zone 156. In an illustratedembodiment, the variable width or size of the extended data zone isdetermined using a margin scheme to reduce the number of tracks basedupon added capacity or BPI of the extended data zone 156 at the outerdiameter relative to the capacity of the inner zone remapped to theextended data zone 156. In one embodiment, the margin scheme reduces thenumber of tracks or size by the equivalent of 2% of the BPI. The schemeis not limited to 2% and other percent of the BPI can be used. Thereduction of the number of tracks or size of the extended data zone z₀156 increases the pad width 155 to increase reliability of the data inthe extended data zone z₀ 156.

In the embodiment illustrated in FIG. 5, firmware 138 for the extendeddata zone z₀ 156 includes an extended data zone background media scancomponent 188. The component 188 is configured to implement an extendeddata zone background media scan to intermittently check the media fordefects to limit data loss proximate to the load/unload area of the discprior to writing data to the extended data zone 156. In an illustratedembodiment, the extended data zone z₀ 156 background media scan isexecuted after a ramp load/unload procedure upon spin up of the disc 104to check for damage. If the scan finds defects, then the extended datazone 156 or portion of the extended data zone 156 is not used for datastorage. The extended data zone 156 is also scanned following aperformance idle, or other period where the heads 102 are located overthe extended data zone 156 prior to executing a write command. Datawritten to the extended data zone 156 is also write verified to enhanceintegrity of the data and limit data loss.

In an illustrated embodiment the firmware 138 also includes a remappingscheme 189 to provide a smooth transition for remapping data from aninner zone z_(n) to the extended data zone z₀ 156. As previouslydiscussed, the recording frequency for the inner zones z_(n) is lowerthan the recording frequency for outer zones z₁ or extended data zone z₀156 as a result of the disc geometry or different tangential velocitiesat the outer diameter 112 relative to the inner diameter 113. Tocompensate for the different recording frequencies, the firmware 138inserts time delays or pads into the inner zone LBA sequence to matchthe recording frequency of the remapped data to the recording frequencyof the extended data zone z₀ 156 to provide a smooth transition forphysical data storage in the extended data zone z₀ 156.

FIGS. 6A-6D schematically illustrate adaptive guard band schemes formultiple heads 102—heads A and head B of a data storage device. In theillustrated embodiments, the multiple heads head A and head B read dataon upper and lower surfaces 190, 192 of disc 104. For read and writeoperations, heads A and B load and unload from ramps A and B. As shown,tolerance variations between heads A and B and ramps A and B providedifferent contact cylinders 146A-B for heads A and B. As schematicallyshown, head A contacts ramp A at contact cylinder 146A and head Bcontacts ramp B at contact cylinder 146B. The contact cylinders146A-146B are used to format different track zeros for heads A and B forextended data storage.

FIGS. 6A-6C progressively illustrate a format scheme for heads A and B.As shown in FIG. 6A, track zero 150-1 for head A is measured the padwidth 145 from the contact cylinder 146A for head A and defines theguard band zone 144 and guard band for head A. In the embodiment shown,the logical block zero cylinder 152 is defined at track zero 150-1 forhead A. In the illustrated embodiment, the adaptive guard band algorithm153 determines available tracks for head B and uses the determination toformat an adapted guard band 154 and extended data storage zone 156 forhead B as progressively illustrated in FIGS. 6B-6C.

As schematically illustrated in FIGS. 6B-6C, the heads A and B arecoupled to an actuator block 118 and move in unison through the actuatormechanism 110. The track zero 150-2 for head B is determined using thecontact cylinder 146B for head B and a no fly zone 196 and cylinder forhead A. The no-fly zone 196 limits the extended data zone z₀ 156 forhead B to avoid contact between head A and the ramp 140 while accessingdata in the extended data zone 156 using head B. As illustrated in FIG.6B, the pad width 145 from the contact cylinder 146B for head B iswithin the no fly zone 196 for head A. Thus, as shown in FIG. 6C, trackzero 150-2 for head B is formatted at the no fly cylinder for head Awhich provides the guard band cylinder for head B. In particular, sincedesignation of track zero 150-2 for head B at pad width 145 is withinthe no-fly zone 196 for head A and would increase the risk of damage tohead A during read/write operations for head B, track zero 150-2 forhead B is formatted at a no fly cylinder for head A to provide theextended data zone z₀ 156 for head B which does not interfere with headA.

In an alternate embodiment illustrated in FIG. 6D, the no fly zone 196for head A does not interfere placement of the track zero 150-2 for headB at the pad width 145 from the contact cylinder 146B for head B. Thus,in the embodiment shown in FIG. 6D, the adaptive guard band cylinder andtrack zero 150-2 are located at the cylinder spaced the pad width 145from the contact cylinder 146B for head B to form the extended data zonez₀ 156 for head B. As previously discussed, in an illustratedembodiment, the extended data zone 156 is used to store higher LBAs fromthe inner zones to reduce the risk of data loss due to placement of theextended data zone z₀ 156 proximate to the load/unload area of theheads.

FIG. 7 illustrates a flow chart for configuring extended data zones 156for multiple heads of a data storage device. As shown in step 200,contact cylinder 146 for the first head is determined. The contactcylinder 146 is the cylinder where the first head contact is detected.As illustrated in step 202, track zero 150-1 for the first head is setat a pad width 145 from the first contact cylinder. Based upon thecontact cylinder, a not fly cylinder is determined in step 204 toprovide a no-fly zone 196 to limit contact with the ramp duringread/write operations utilizing the other heads. In step 206, thecontact cylinder 146 for the next head is determined. As shown in step208, if a cylinder at a pad width 145 from the contact cylinder 146 doesnot interfere with the no fly zone 196 of the first head, the padcylinder is used to format track zero 150 and the extended data zone z₀156 for the next head. If the pad cylinder does interfere with the nofly zone 196, then the no fly cylinder is used to format track zero 150and the extended data zone 156 in step 210. Steps 206-210 are repeatedfor each head of the head stack to configure track zero 150 and theextended data storage zone 156 or adaptive guard band for the multipleheads of the data storage device.

FIGS. 8A-8B illustrate embodiments of a device including multiple headsA-D (schematically shown) configured to read and write data to upper andlower recording surfaces 190, 192 of discs 104-1, 104-2. Heads A and Bread data from upper and lower surfaces 190, 192 of disc 104-1 and headsC and D read data from upper and lower surfaces 190, 192 of disc 104-2.The vertically aligned tracks on each of the discs 104-1, 104-2 formsthe cylinders of the disc stack. In the illustrated embodiment, data isstored to a plurality of vertically aligned tracks or cylinders in aserpents storage pattern as shown. The serpent pattern enhancessequential data rates by switching between adjacent tracks and headswithin a particular zone to limit access time and movement of theactuator block 118 (not shown). Each zone z₁-z_(n) includes multipleserpent paths to facilitate efficient data storage and retrieval. Thefirmware of the device assigns LBAs to adjacent tracks for differentheads in a serpent path to provide the serpent storage pattern asillustrated in FIGS. 8A-8B. Although FIGS. 8A-8B illustrate oneparticular serpent path pattern, application is not limited to theparticular serpent pattern shown.

FIGS. 8A-8B illustrate different embodiments for configuring track zeroand extended data zones 156 for heads A-D. Tracks 114 are schematicallyillustrated as blocks in FIGS. 8A-8B for illustration purposes. Asshown, track zero 150-1 is defined based upon the contact cylinder forhead C. In the embodiments shown, heads A, B and D have tracks available(schematically illustrated as blocks) for extended data storage outwardfrom 1 track zero 150-1 for—head C. The available tracks are determinedbased upon the contact cylinder for heads A, B and D and required padwidth 145 from the contact cylinder 146 for heads A, B and D or no flycylinder or zone 196 for head C as previously described. In theembodiment shown in FIG. 8A, the device is formatted to provide trackzero 150-2 for heads A, B and D spaced from track zero 150-1 for head Cand an extended serpent path So including available tracks for heads A,B and D to define an adaptive guard band for heads A, B and D and theextended data storage zone z₀ 156 for heads A, B and D.

In another embodiment illustrated in FIG. 8B, the device is formatted toprovide extended serpent path S₀ utilizing available tracks for heads Band D to define track zero 150-2 for heads B and D and extended datazone 156 z₀ for heads B and D to optimize use of the available tracksfor heads A-D. In the embodiment illustrated in FIG. 8B, use of heads Band D provides optimum uses of the available tracks for a device havingone extended track zero 150-2 for heads A-D. FIG. 8B provides optimumuse of the available tracks for data storage since as schematicallyshown, the serpent path(s) or pattern utilizes more of the availabletracks for heads A, B, D for extended data storage. The firmware 138 oralgorithm for formatting the multiple heads for extended data storagecan include instructions or code for tuning the extended data zone z₀156 for optimum data storage capacity, efficiency and read/write time asillustrated in FIG. 9.

FIG. 9 illustrates steps for tuning the extended data storage for thedevice. As shown in FIG. 9, the contact cylinders for each head aredetermined in step 220. The contact cylinder for the first head tocontact the ramp is used to set track zero 150-1 in step 222. In step224, the cylinders spaced a pad width from the contact cylinder for eachheads (and spaced from no fly cylinder as previously described) are usedto determine available tracks between the pad cylinder and track zero150-1. The algorithm 153 uses the pad cylinders for each of the heads asthe track zero to calculate different serpent paths or patterns for eachpossible track zero in step 226. Thus, as illustrated with respect toFIG. 8A, pad cylinder for head A is used as the track zero 150-2 andextended data storage for heads A, B and D at extended track zero 150-2is determined. Next the algorithm repeats the calculation for head Bwhere the pad cylinder for head B is used as the extended track zero150-2 as illustrated in FIG. 8B and the available serpent paths arecalculated. In step 228, the track zero 150-2 providing the optimumextended data storage capacity is selected as track zero 150-2 to formatthe discs or data storage media.

FIGS. 10A-10B illustrate embodiments of a multiple head device having aplurality of track zero 150-1, 150-2, 150-3 for heads A-D. In theembodiment illustrated in FIG. 10A, the device includes a first trackzero 150-1 for head C, a second track zero 150-2 for head A and a thirdtrack zero 150-3 for heads B and D. The track zero 150-2 is physicallylocated at a cylinder spaced outwardly of track zero 150-1 for head Cand the track zero 150-3 is physically located at a cylinder spacedoutwardly from the track zero 150-2 for head A. As shown in FIG. 10A, afirst extended zone between track zero 150-1 and track zero 150-2 forhead C includes a serpent pattern S₀₁ (illustrated schematically)including heads A, B and D and a second extended data zone betweenextended track zero 150-3 and track zero 150-2 includes a serpentpattern S₀₂ including heads B and D to optimize data storage foravailable extended data tracks.

In the embodiment illustrated in FIG. 10B, the plurality of extendedtrack zeros for heads A-D includes track zero 150-1 for head C, trackzero 150-2 for head A and track zero 150-3 for head B and track zero150-4 for head D. As shown, track zero 150-2 is radially spaced fromtrack zero 150-1, track zero 150-3 is radially spaced from track zero150-2 and track zero 150-4 is radially spaced from track zero 150-3. Asshown, a serpent pattern S₀₁ for heads A, B and D is formatted for afirst extended data zone at track zero 150-2, a second serpent patternS₀₂ for heads B and D is formatted for a second extended data zone attrack zero 150-3. Serpent pattern S₀₃ for head D is formatted at a thirdextended data zone at extended track zero 150-4. The multiple extendedtrack zeros optimize use of available tracks for increased data storage.

Embodiments of the present application have application for devicesimplementing variable bit rate aspect ratios for different heads ormedia to enhance data storage capacity of the device. It is to beunderstood that even though numerous characteristics and advantages ofvarious embodiments of the invention have been set forth in theforegoing description, together with details of the structure andfunction of various embodiments of the invention, this disclosure isillustrative only, and changes may be made in detail, especially inmatters of structure and arrangement of parts within the principles ofthe present invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed. Forexample, the particular elements may vary depending on the particularapplication while maintaining substantially the same functionalitywithout departing from the scope and spirit of the present invention. Inaddition, although the embodiments described herein are directed toparticular examples it will be appreciated by those skilled in the artthat the teachings of the present invention are not limited to theparticular examples and other embodiments can be implemented withoutdeparting from the scope and spirit of the present invention.

What is claimed is:
 1. An assembly comprising: a first head configuredto read or write data to a first recording media surface; a second headconfigured to read or write data to a second recording media surface;and instructions stored in memory and implemented through a controllerassembly to store data to a first extended data zone on the firstrecording media surface beginning at a first track zero at a firstcylinder and extending to a first logical block zero cylinder on thefirst recording media surface, and store data to a second extended datazone on the second recording media surface beginning at a second trackzero at a second cylinder different from the first cylinder andextending to a second logical block zero cylinder on the secondrecording media surface, wherein the first and second extended datazones are within a designated guard band zone, wherein the first logicalblock zero cylinder corresponds to a first track on the first recordingmedia surface accessed by a host to read or write data, wherein thesecond logical block zero cylinder corresponds to a first track on thesecond recording media surface accessed by the host to read or writedata.
 2. The assembly of claim 1 wherein the first and second recordingmedia surfaces comprise opposing sides of a single recording disc. 3.The assembly of claim 2 wherein the single recording disc comprises aradius, an outer diameter and an inner diameter, and wherein the firstcylinder and the second cylinder are positioned between the innerdiameter and the outer diameter, and wherein the second cylinder isspaced radially outwardly towards the outer diameter of the singlerecording disc from the first cylinder.
 4. The assembly of claim 2wherein the first track zero is spaced a first pad width along a radiusof the single recording disc from a first contact cylinder where thefirst head contacts a first load/unload ramp and the second track zerois spaced a second pad width along the radius of the single recordingdisc from a second contact cylinder where the second head contacts asecond load/unload ramp, and wherein the first pad width is a widthalong the radius within a first guard band zone on the first recordingmedia surface, the first guard band zone being between the first contactcylinder and the first track zero and comprising tracks on which no datastorage by the first head is permitted, and wherein the second pad widthis a width along the radius within a second guard band zone, the secondguard band zone being between the second contact cylinder and the secondtrack zero and comprising tracks on which no data storage by the secondhead is permitted.
 5. The assembly of claim 2 wherein the singlerecording disc comprises a radius, an inner diameter and an outerdiameter, and wherein the assembly further comprises: a first contactcylinder where the first head contacts a load/unload ramp, the firstcontact cylinder being proximate to the outer diameter, wherein thefirst track zero is positioned radially inwardly from the first contactcylinder; the designated guard band zone being divided into a firstregion having tracks on which no data storage by the first head ispermitted and a second region positioned radially inwardly from thefirst region having tracks on which data storage by the first head ispermitted; and a no fly cylinder for the first head positionedsubstantially at a junction between the first region and the secondregion, wherein the first track zero is defined at the no fly cylinderfor the first head.
 6. The assembly of claim 1 and comprising a thirdhead configured to read or write data to a third recording media surfaceand the instructions are configured to store data to the third recordingmedia surface beginning at a third logical block zero cylinder.
 7. Theassembly of claim 6 wherein the instructions format an extended datazone between a third track zero at a third cylinder and the thirdlogical block zero for the third head on the third recording mediasurface.
 8. The assembly of claim 7 wherein each of the extended datazones includes one or more serpent paths utilizing tracks.
 9. Theassembly of claim 1 wherein the designated guard band zone comprisescylinders used for a load/unload operation.
 10. The assembly of claim 1and comprising a third head where the third head has a third track zeroat a third cylinder spaced from the first and second cylinders.
 11. Anassembly comprising: a guard band algorithm including instructionsstored on one or more hardware components implemented through acontroller assembly to format a first extended data zone beginning at afirst track zero at a first cylinder and extending to a first logicalblock zero cylinder on a first recording media surface, and to format asecond extended data zone on a second recording media surface beginningat a second track zero at a second cylinder different from the firstcylinder and extending to a second logical block zero cylinder, whereinthe first and second extended data zones are within a designated guardband zone wherein the first logical block zero cylinder corresponds to afirst track on the first recording media surface accessed by a host toread or write data, and wherein the second logical block zero cylindercorresponds to a first track on the second recording media surfaceaccessed by the host to read or write data.
 12. The assembly of claim 11where the first and second recording media surfaces are upper and lowersurfaces of a single data storage disc.
 13. A method comprising:formatting a first head track zero at a first cylinder spaced between afirst contact cylinder where a first head contacts a first load/unloadramp and a first logical block zero cylinder on a first recordingsurface to form a first extended data zone on the first recordingsurface; and formatting a second head track zero at a second cylinderspaced from the first cylinder to provide an extended data zone for asecond head between the second head track zero at the second cylinderand a second logical block zero cylinder on a second recording surfaceto form a second extended data zone on the second recording surface,wherein the first logical block zero cylinder corresponds to a firsttrack on a first recording media surface accessed by a host to read orwrite data, and wherein the second logical block zero cylindercorresponds to a first track on a second recording media surfaceaccessed by the host to read or write data, and wherein the first andsecond extended data zones are within a designated guard band zone. 14.The method of claim 13, wherein the first and second recording mediasurfaces are provided on opposing sides of a single recording disc, andwherein the step of formatting the first head track zero at the firstcylinder and the second head track zero at the second cylinder for thefirst and second heads comprises: determining the first contact cylinderwhere the first head contacts the first load/unload ramp; formatting thefirst head track zero at a first pad width along a radius of the singlerecording disc from the first contact cylinder; determining a secondcontact cylinder where the second head contacts a second load/unloadramp; and formatting the second head track zero at a second pad widthalong the radius of the single recording disc from the second contactcylinder, wherein the first pad width is a width along the radius withina first guard band zone on the first recording media surface, the firstguard band zone being between the first contact cylinder and the firsttrack zero and comprising tracks on which no data storage by the firsthead is permitted, and wherein the second pad width is a width along theradius within a second guard band zone, the second guard band zone beingbetween the second contact cylinder and the second track zero andcomprising tracks on which no data storage by the second head ispermitted.
 15. The method of claim 13 and comprising: providing thefirst and second recording media surfaces on opposing sides of a singlerecording disc having a radius, an outer diameter and an inner diameter;determining the first contact cylinder where the first head contacts thefirst load/unload ramp proximate to the outer diameter, wherein thefirst track zero is positioned radially inwardly from the first contactcylinder; determining a first guard band zone between the first contactcylinder and the first track zero, the first guard band zone beingdivided into a first region having tracks on which no data storage bythe first head is permitted and a second region positioned radiallyinwardly from the first region having tracks on which data storage bythe first head is permitted; and defining a no fly cylinder for thefirst head substantially at a junction between the first region and thesecond region; and formatting the second head track zero for the secondhead at the no fly cylinder for the first head.
 16. The method of claim13 and comprising: providing the first and second recording mediasurfaces on opposing sides of a single recording disc having a radius,an outer diameter and an inner diameter; and formatting the second headtrack zero for the second head at a second pad width from a secondcontact cylinder where the second head contacts a second load/unloadramp, wherein the second pad width is a width along the radius within asecond guard band zone, the second guard band zone being between thesecond contact cylinder and the second head track zero and comprisingtracks on which no data storage by the second head is permitted.
 17. Themethod of claim 13 and comprising: formatting a third head track zerofor a third head at a third cylinder spaced from the first and secondcylinders.
 18. The method of claim 13 and comprising; formatting a thirdhead track zero for a third head at one of the first and secondcylinders.
 19. The method of claim 13 and comprising: determiningavailable tracks for the second head and a third head between second andthird contact cylinders for the second and third heads and the firsthead track zero, wherein the second contact cylinder for the second headis a cylinder located where the second head contacts a secondload/unload ramp, and wherein the third contact cylinder for the thirdhead is a cylinder located where the third head contacts a thirdload/unload ramp; and formatting the second head track zero and a thirdhead track zero at the second cylinder providing a largest number ofextended serpent tracks for both the second and third heads to optimizeextended data storage.